Corrections and Clarifications: A previous version of this article incorrectly identified the group involved in this week's protests in Janesville, Wis.

JANESVILLE, Wis. — As GOP frontrunner Donald Trump prepared to speak to supporters in Wisconsin on Tuesday, a 15-year-old girl outside the venue was pepper-sprayed after striking another bystander, police said.

Police said the girl was peppered-sprayed in the crowd by a non-law enforcement person. Hundreds of anti-Trump protesters and supporters had gathered outside the Holiday Inn Express in southern Wisconsin, where Trump was holding his maiden rally in the state ahead of Tuesday's primary.

In video posted on social media of the tense scene, the teen appears to be arguing with a middle-aged man and shoves or punches him before the pepper spray is deployed by a second man. The girl appears to hold a sign that accuses Trump of supporting white supremacy. She is standing next to another young woman holding a Black Lives Matter sign. Others in the crowd could be heard chanting, "All lives matter."

Police said they are reviewing several videos taken at the scene and have spoken to several eyewitnesses. The young woman told officers she was groped by a man before pushing him away, police said in a statement.

The department on Wednesday published a photo of a young man wearing a red "Make America Great Again" baseball cap who they want to question about the incident. Police asked the public with help identifying the man.

Janesville Police Chief David Moore said Wednesday that the investigation has been turned over to the department's bureau of detectives. "We intend to learn the true events that occurred and make the appropriate arrests," he said.

On Monday, six protesters were arrested on charges of disorderly conduct, obstructing an officer and trespass after refusing to leave the lobby of the Holiday Inn Express as part of another anti-Trump protest at the venue, police said.

Police said the protesters identified themselves as belonging to the group Showing Up for Racial Justice. Members of the group had locked themselves together inside of PVC piping before occupying the lobby area. About 60 other protesters who entered the lobby left the hotel at the request of police.

No photo of the punch, but here's a photo of the pepper spray. Woman received medical treatment, police said. pic.twitter.com/1EOyBbAWQz

Trump has faced criticism from rivals that the tenor of his campaign has created an unsafe environment at his rallies.

Earlier this month, Trump abruptly canceled an event in Chicago out of safety concerns after hundreds of protesters filled the arena where he was scheduled to speak. In another incident this month, a 78-year-old man was charged with assault and disorderly conduct after he sucker-punched a protester during a rally in Fayetteville, N.C.

Inside the hotel conference center, Trump on Tuesday dismissed Wisconsin Gov. Scott Walker as an ineffective leader, arguing that the Badger State governor has been a poor steward of the state's economy.

Trump went after Walker hours after the Wisconsin governor threw his support behind Texas Sen. Ted Cruz for the GOP presidential nomination.

"By the summer of 2015, Wisconsin was facing a $2.2 billion, two-year budget deficit," Trump said. "That's terrible ...Twenty thousand fewer people in Wisconsin's labor force than seven years ago even though the population has grown by 100,000."

Polls show that the race for Wisconsin is tight, and a win for Cruz would go a long way in complicating Trump’s hopes to win the nomination outright before the party’s national convention in Cleveland this summer.

Gov. John Kasich is polling a distant third. But because the state’s 42 delegates are allocated on the basis of state and congressional district winners, the Ohio governor’s showing could have a significant impact on shaping the GOP race ahead of several winner-take-all contests coming up.

The rally in Janesville, home of Republican House Speaker Paul Ryan, marked Trump’s kickoff campaign event ahead of next week’s Wisconsin primary. Cruz and Kasich have been campaigning throughout the state for days. Trump says he’s planning to spend much of this week with rallies planned in Appleton and Green Bay.

"If we win Wisconsin, it's over," Trump said

Trump arrived in Wisconsin on a day when his campaign faces plenty of headwind.

His campaign manager, Corey Lewandowski, was charged with simple battery for an altercation with a reporter in Florida earlier this month. Trump, however, says the allegations against Lewandowski are baseless and charged that the reporter, Michelle Fields, greatly exaggerated what happened.

"Don't forget, initially she said 'thrown to the floor,'" Trump said. "If somebody squeezed your arm or hurt you wouldn't you start screaming or something? Did you see any change in her face?"

"(Lewandowski) has got a beautiful wife and children," Trump added. "I'm not going to destroy a man for that."

The New York businessman also faced a trio of tough interviews on conservative talk radio Monday, including sharp criticism from influential talk show host Charlie Sykes, who told Trump he sounded like a “12-year-old bully on the playground” with his threats to go after Cruz’s wife.

Trump made his threats after an anti-Trump Super PAC ran an ad with a nude photograph of Trump’s wife, Melania, a former model, ahead of the March 22 Utah caucuses. Cruz has accused Trump’s “henchmen” of engineering a National Enquirer story saying the senator is being investigated for extramarital affairs.

In his comments to supporters Tuesday, Trump steered clear of the war of the words with Cruz over their spouses, but he resurrected questions about the Texas senator's eligibility to run for president because he was born in Canada. Cruz maintains he meets the criteria of "natural-born" citizen because his mother is American-born. Several lawsuits by voters, including suits brought in Illinois and Indiana, on the issue have been tossed.

"The first thing that's going to happen (if Cruz wins the nomination) is that the Democrats are going to sue Ted Cruz," Trump said. "Remember this, if he gets the nomination, within the first few days, he will be sued from the Democrats that he doesn't have the right to be president. And I think they're right."